Thermostat



"I A. A. STRAND 2,075,873

THERMOSTAT 5 Sheets-Sheet 1 Filed Oct. 20, 1951 A. A. STRAND A ril 6,1937.

THERMOS TAT Filed Oct. 20, 1951 3 Sheets-Sheet 2 INVENTOR ATTORNEY-3 BYhis Patented Apr. 6, 1937' rnaamosmr August A. Strand, Maiden, Mass.,assignor to G and N Engineering Company, Boston, Mass., a corporation ofMassachusetts Application October 20, 1931, Serial No. 569,916

15 Claims. (01. 1753l5) The invention relates to controllingtemperature, and more particularly to thermostats.

The objects of the invention include the provision of a relativelyinexpensive, dependable, highly efficient and sensitive device of thetype above indicated. Various further and more specific objects,features and advantages will clearly appear from the detaileddescription given below, taken in connection with the accompanyingdrawings which form a part of this specification and illustrate, merelyby way of example, embodiments of the invention. a

In the drawings, Fig. 1 represents a front elevation of the thermostatwith the cover removed;

Fig. 2- is a section taken on the line 2-2 of Fig. 1;

Fig. 3 is a detail taken on the line 33 of Fig. 1, illustrating theconstruction of a part of the device;

Fig. 4 represents a section on the line 44 of Fig. 1; Fig. 5 is asection on the line 5-5 of Fig. 4;

Fig. 6 is a section taken on the line 6-6 of Fig. 1;

Fig. 7 is a section on the line 1-1 of Fig. 1;

Fig. 8 is a section on the line 8-8 of Fig. 2;

Fig. 9 is a detail showing the manner in which the thermostat may bemounted on a wall;

Fig. 10 represents diagrammatically the wiring diagram of thethermostat;

Fig. 11 is a detail illustrating a modified form of the contacts.

Figs. 1 2 and 13 illustrate, on an enlarged scale, the manner of sealingthe temperature-responsive units.

In the following description and in the claims, various details will beidentified by specific names for convenience, but they are intended tobe as generic in their application as the art will permit.

Like reference characters denote like parts in the several figures ofthe drawings.

In the drawings accompanying and forming part of this specification,certain specific disclosures ofthe invention are made for purposes ofexplanation, but it will be understood that the details may be modifiedin various respects with out departure from the broad aspect of theinvention.

Referring rfiiw to the drawings, the thermostat comprises a metal base44 having a removable cover 45 secured thereto in any desired manner.The removable cover 45 may have the usual, ordinary thermometer 46secured thereto.

Secured to the base 44 is a bracket 41, a lower insulating plate 48 andan upper insulating plate I5.

Secured to the bracket 41 is a bellows 20 constructed to expand upon arise in temperature and to contract upon a drop in temperature. Thebellows shown comprises a plurality of sections 49 of a similarconstruction, each section having a socket 5I secured on one side and aplug 50 secured to the other. These sections are screwed together withthe plugs fitting in the sockets and, if desired, washers 52 may beinterposed between the plugs and sockets, as indicated.

Each section 49 is made up of two circular discs I49 and I50 overlappedand soldered together around their periphery. These discs may be made ofgood temperature conducting material such as copper and, as shown, arecorrugated annularly with the corrugations increasing in size (becomingflatter) from the circumference to the center. These discs I49 and I50are suitably soldered to the plugs and sockets, as shown.

Each section 49 may be filled with a suitable temperature responsivemedium such as ether. The ether is introduced preferably through anopening in the plug which is sealed by a ball of lead shot placed in theopening after the section is filled. The soft metal of the shot isexpanded in the opening and the metal of the plug 50 is spun over asshown to make a gas tight joint, Fig. 12 representing the relation ofthe parts prior to the spinning operation and Fig. 13

representing the relation of the parts after the spinning operation. Thespinning tool is denoted It will be noted that the ball250 is pressedagainst the tapered surface 25I on the plug and that the reduced upperend 252 is spun down on the ball 250. A double seal is thereby providedat these points. I

The top section of bellows 20 is secured to the bracket 41 by a fittingI5I threaded on the plug 5|. The lower section of bellows 29 has a rod54 soldered in the socket 50, the rod 54 passing through an opening I54in the bracket 41. A coil spring 56 may be interposed between the lowersection 49 and the bracket.

The rod 54 has an oiIset portion 55 (Fig. 5) which straddles the hollowshaft 59. To form a rack-and-pinion connection between the rod 54 andthe shaft 59 whereby small longitudinal movement of the rod 54 due totemperature changes causes a large rotary movement in the shaft 59, aflexible round wire, or fiat band 51, as shown, is wrapped around theshaft 59 with a single turn, as shown, or with a plurality of turns, andis held taut by a coil spring 58, the band 51 and spring 58 beingsecured to the bent ends of the ofiset 55.

It will be noted that the ends of the ofiset 55 5 are so located withrespect to the hollow shaft 59 that the adjacent parts of the flat bend51 on the shaft do not touch each other (Fig. 2).

Also supported by the bracket 41 is an insulating drum or disc 68mounted upon a bushing 81 which passes through a bearing inthe dependingpart H! of the bracket. Fixedly secured to the bushing 8'! is a gearmember 84 having teeth 85 which mesh an adjusting member 88 whichprojects out through an opening inthe cover 45 so that the discs 84 and88 may be adjusted for the desired temperature. If desired, the gearmember 84 may be calibrated in degrees of temperature.

The insulating disc 88 has a pair of spiral contacts 24 and 25 partiallyimbedded therein, as illustrated best in Figs. 1, 2 and 18. Betweenthese contacts is a ridge 28 of insulating material which is normallyheld abovethe surface of the contacts, as shown in Fig. 3 by a spring18, to provide a 25 yieldable resistance to the roller 28 on the rotaryarm 21. A limiting member I18 secured to the disc 88 limits theretracting movement of ridge 28 to a position flush with the outersurfaces of the spiral contacts 24 and 25 to prevent all pos- 30sibility of the roller 28 bridging the contacts 24 and 25.

The insulating disc 88 also has a pair of circular collector rings 22and 23 in the periphery thereof, ring 22 being connected to the contact25 and ring 23 being connected to the contact 24.

Journalled within the bushing 81 and a depending part 88 of the bracket41 is a rod 2| upon which is mounted the hollow shaft 53. The latter hasits ends flanged inwardly 'so that it 40 contacts the rod 2| at thesepoints only to cut down friction. Mounted upon the shaft 58 isinsulating ring 62 which carries a collector ring 29 to which the rigidarm 21 is secured. The arm 27 carries a grooved roller 28 which isrotatable thereon and movable axially thereon and which runs upon thespiral contacts 24 and 25. Spring members 83 and 89 hold the roller 28in contact with the spiral contacts 24 and 25. A brush 38 (Figs. 4 and8) is secured to the insulating base 48 and contacts the collector ring28.

Also mounted upon the insulating base 48 is a pair of electro-magnets 3|and 32 having the reduced ends of their cores 12 riveted over on theopposite side of the insulating base (Fig. '7). A

brass holder 13 has openings through which the cores 12 pass and assistsin holding the windings of the electro-magnets 3| and 32 against theinsulating base 48, a screw I48 holding the brass holder to the base(Fig. 8).

The armature 34 is pivoted to the holder 13 by pivot 33 and has securedthereto a pivot 88 (Fig. 7) which connects with a connecting rod 8|which in turn is pivoted to an arm 82 mounted on shait83 which isjournalled in a fitting 84 secured to the insulating base 48. The shaft83 has an arm 85 which connects with a link 88 which is pivoted to thecenter of an insulating bar 38 (Fig. 6).

The insulating bar 38 is pivoted toa fitting I88 which is secured tothe, insulating base and carries a circular contact 38 which engagesstationary contacts 48 secured to the insulating base.

For giving a snap action to the switch 33, 48

a rod 81 is pivoted to theinsulating member 38 and loosely passesthrough a fulcrum member 88 and through an opening in fitting 88 whichis secured to an insulating base 48. A spring I88 operating between ashoulder upon the rod 81 and the fulcrum piece 88 insures a quick snapof the movable contact 38 for opening and closing.

Secured to the bracket 41 is an insulating panel 14 (Figs. 1 and 7). Tothis panel are pivoted contacts 36 and 31 which in turn are pivotallyconnected toan insulating link 35 which is secured to a pivot 15, inturn secured to the armature 34. The contacts or brushes 38 and 31 havecurved ends for alternately engaging and disengaging the collector rings22 and 23, as indicated in Figs. 2 and 7.

It will be noted that the three binding posts, indicated by 42 (Figs. 6and 2), are mounted upon the insulating base 48 and connect with themagnets 3| and 32 and with the brush 38, and contacts 48, as indicatedin Fig. 10, which illustrates diagrammatically the thermostat and theelectrical wiring thereof.

If desired, the binding posts 42 may be connected by wires 18 to thethree prongs of the connector, illustrated by I42 in Fig. 9, which maybe mounted upon the upper insulating base 15, as illustrated in Figs. 2and 9, and the other part of the connector 43 may form a wall receptacle(Fig. 9) by which the entire thermostat may be mounted.

The contacts on the wall receptacle may lead to the source of power andthe load, as illustrated in Fig. 10. The load may be a distantelectromagnet for operating the controls of a heating or cooling systemor, in the case of electrical heating, the load may be the heater unitsthemselves.

If desired, the connectors 43 and I42 may be omitted and the connectingwires to the power source and load may lead to these devices directly inwhich case the thermostat may be supported from the wall or othersupport in any conventional manner.

The operation of the thermostat is as follows: Referring to Fig. 10 andassuming the room to drop below its desired temperature, the bellows 28will contract and the arm 21 will move, say, to the left. As the roller28 engages the spring pressed insulating piece 28, it will depress it toa position flush with the outer edges of the spiral contacts 24 and 25with the result that the spring pressure on the insulating piece 28 willcause the roller 28 to make a quick make with the contact 24. Thiscompletes the circuit through the collector ring 23, brush 38, which isin engagement therewith, operating magnet 32 to close the contacts 38,48 and apply energy to the load. This provides more heat, raising thetemperature of the room.

It will be seen that the operation of the magnet 32 breaks the contactat 38 and makes the contact at 31 so that the circuit through spiralcontact 25 will be in readiness when the circuit is completed byoperation of the roller 28 back to the position shown.

As the temperature of the room increases, the bellows 28 will expand andmove the arm 21 back across the spring pressed insulating piece 28 tothe position shown in Fig. 18, which will establish a circuit throughmagnet 3| to open the contacts 39, 48 and thereby turn off the-heat.This cycle of events will continue, to keep the temperaturesubstantially constant;

It will be appreciated that the current through the electro-magnets 3|and 32 lasts only for an instant and therefore there is no chance forthem to become hot and interfere with the operation of the thermostat.Furthermore, the roller 28 never breaks a circuit, all breaking beingdone by the brushes 36 and 31. The roller 28 merely operates to make acircuit. Thus, no arcing, which may interfere with radio, can take placesince the make of contact 28 is always quick due to the snap action ofspring pressed insulating piece 26, and the break of the brushes in 36and 31 is always quick due to the quick action of the arm 38 whichoperates these members.

To adjust the thermostat to a different operating temperature it is onlynecessary to move the gear 66 to move the disc 64 to set the desired istemperature. Thus, a wide range of operating conditions is provided for.The thermostat may be used to keep a room, say, at '70 degrees and then,if desired, by merely making the adjustment stated above, the thermostatmay be set to keep a temperature of, say, degrees. The long length ofspiral of the contacts 24 and 25 allows a great range of movement forthe roller 28. The thermostat is suitable for regulating temperatureboth in buildings and in refrigerators.

Another advantage of the present construction is that it may be useddirectly on household voltages in the neighborhood of 110 volts and thatit is not necessary to provide dry cells or local sources of current ofreduced voltage.

The construction of the multiple unit bellows provides a largetemperature control surface and the corrugated construction of each unitassists inproviding a bellows which is extremely sensitive to minutechanges in (temperature. Furthermore, the connection between the bellowsand the thermostat arm is such as to greatly multiply the movement ofthe bellows to make the arm move a substantial distance when thetemperature varies a fraction of a degree.

The provision of the hollow shaft 59 supported on the rod 2| at its endsonly, the spacing of adjacent parts of the convolutions of the band 51on the shaft 59 and the loose sliding fit of the bellows rod 54 throughthe opening in the bracket, all assist in cutting down friction in theoperating parts to a minimum and thereby greatly increasing thesensitivity of the instrument.

It will be understood that in some cases the switch 39, 40 may be placedaway fromthe thermostat, near the apparatus it is desired to control, orboth the electromagnets 3|, 32 switch 39, 40 and brushes 36, 31 may belocated away from the thermostat.

The construction of the bellows is such that a substantially uniformrate of linear expansion of the bellows per degree change in temperatureis obtained.

If desired, instead of using the snap contact arrangement for the roller28 above described, the arrangement shown in Fig. 11 may be used. Inthis figure the spiral contacts 2| and 25 are merely spaced apart by afixed piece of insulation .200 and an additional roller 26! is placedupon the arm 21 riding on the face of the insulating disc in a circularpath. A spring pressed piece 203 may. be placed in the path opposite thesection of insulation 260. Thus, the operation of the spring pressedpiece 203 against the roller 20! on the rigid arm 21 operates to snapthe contact roller 28 from one spiral segment to the other. The piece203 may be constructed and spring actuated in a manner similar to thepiece 26 except that it need not be made of insulation.

while certain novel features of the invention have been disclosed andare pointed out in the annexed claims, it'will be understood thatvarious omissions, substitutions and changes may be made by thoseskilled in the art without departing from the spirit of the invention.

What is claimed is:

1. In a thermostat, a base, a temperature responsive bellows securedrigidly to said base at one end and having a rod at its other end, ashaft rotatably mounted on said base, a contact on said shaft, aflexible member wrapped around said shaft and connected to said rodwhereby longitudinal movement of said bellows imparts rotation to saidshaft, and a contact adapted to be engaged by said first contact.

2. In a thermostat, a temperature responsive device adapted to expandand contract longitudinally, a rotary element, connections between saidtemperature responsive device and said rotary element whereby theperipheral movement of said rotary element is substantially equal to thelinear movement of said device, means cooperating with said rotaryelement to control an electrical circuit, and means comprising a spiral7 contact for controlling the path of said rotary element.

3. In a thermostat, a temperature responsive device adapted to expandand contract longitudinally, a rotary contact member, connectionsbetween said temperature responsive device and said rotary contactmember for transmitting movement therebetween, a second contact membercooperating with said rotary contact member to control an electricalcircuit, and means for adjusting one of said contact members for desiredtemperature conditions.

4. In a thermostat, a temperature responsive device adapted to expandand contract, a rotary element, a flexible member wrapped around saidrotary element and secured to said device to transmit motion from saiddevice to said rotary element, and heat controlling devices operated bysaid rotary element.

5. In a thermostat, a base, a temperature responsive bellows comprisinga plurality of disclike units arranged in line, said bellows beingsecured rigidly to said base at one end and having a rod at its otherend, an insulating disc rotatably mounted on said base, a plurality ofspiral contacts on said insulating disc and a spring pressed insulatingpiece therebetween, an electric circuit controlled by said contacts, aplurality of collector rings on the periphery of said disc and connectedto said contacts, a shaft rotatably mounted on said base, a rigid armprojecting from said shaft, a grooved roller rotatable and slidable onsaid arm riding on said spiral contacts, a strand wrapped around saidshaft and connected to said rod whereby longitudinal movement of saidbellows imparts rotation to said arm, an electromagnet in said circuitoperated by engagement of said roller and said contacts and brushesengaged with said collector rings and operated by said electromagnet.

6. In a thermostat, a rotary support member, spiral contacts on saidsupport member, an insulating member between said contacts, a rotary armmember, a contact element slidably mounted on said arm.member andengaging said contacts, and temperature responsive means for impartingmovement to one of said members and means for adjusting the other memberto set a desired temperature.

7. In a thermostat, a support having contacts thereon, a contact memberengaging said support and means whereby said contact member is roiii 40brushes adapted to engage and disengage with tated relative to saidsupport through an extent substantially greater than 360 degrees over anon-reentrant path to engage said contacts.

8. In combination, a support, contacts on said support, an insulatingmember between said contacts, means for yieldably urging said insulatingmember outwardly, a contact member and means for imparting relativemovement to said contacts and contact member to cause said insulatingmember to shift engagement of said contact member from one contact tothe other with a snap movement.

Q/l'n a thermostat, a drum having a plurality of peripheral collectorrings, brushes adapted to engage and disengage with said collectorrings,

an electric circuit, an electromagnet in said circuit for operating saidbrushes to make contact between one brush and one ring andsimultaneously to break contact between the other brush and the otherring, and thermostat contacting devices in said circuit responsive tochanges in temperature for operating said electromagnet, saidelectromagnet being controlled by said brushes and contacting devices,parts of said contacting devices being mounted on said drum.

10. In a thermostat, a support, spiral contacts on said support, anopening in said support between said contacts, an insulating memberslidably mounted in said opening, a spring for yieldably urging saidinsulating member outwardly, limiting means to prevent said insulatingmember from retracting below the surface of said contacts, a rotary arm,a grooved roller rotatably and slidably mounted on said arm and engagingsaid contacts, and temperature responsive means for imparting relativerotation between saidarm and support.

11. In a thermostat, a plurality of terminals, an electric' circuitconnected to said terminals,

said terminals, an electromagnet device in said circuit cooperating withsaid brushes and terminals to make contact between one brush and oneterminal and simultaneously to break contact be- 45 tween the otherbrush and the other terminal,

50 said contacting devices and thermostat contacting devices responsiveto changes in temperature for closing said circuit abruptly to operatesaid electromagnet devices, said electromagnet devices being controlledby terminals.

12. In a thermostat, a pair of electromagnets,

and by said brushes andan armature operated thereby, a drum, 8. pair ofconducting rings mounted thereon, a pair of brushes engageable with saidconducting elements, connections between said brushes and said armaturefor alternately engaging a brush with a ring, a pair of contacts mountedon said drum and connected to said rings, respectively, a contact memberadapted to alternately engage said contacts and operable by change intemperature, means whereby said electromagnets are selectively operatedby the make 01' said contact member and said contacts and to cause thecurrent in that circuit to be broken at said brushes.

13. In a thermostat, a pair of electromagnets, an armature operatedthereby, a drum having a pair of collector rings, a. pair of brushesengageable with said collector rings, connections between said brushesand said armature for alternately engaging one brush with one ring anddisengaging the other brush from the other ring, a pair of contactsmounted on said drum and connected to said rings, respectively, a"contact member adapted to alternately engage said contacts and operableby change in temperature, connections from said brushes to the windingsof said electromagnets and to said contact member whereby saidelectromagnets are selectively operated by the make of said contactmember and one 01' said contacts and such operation immediately causesthe current in that circuit to be broken at said brushes, 2. switchcontrolled by said electromagnets, and means for adjusting said drum forthe desired temperature.

14. In a thermostat, a contacting element, two contact members, twoelectrical circuits, means to cause said element to engage either one ofsaid members abruptly to complete one of said circuits, and means insaid circuits responsive to the current therein to break whichever saidcircuit has been completed.

15. A thermostat comprising a temperature responsive device having oneend anchored and the other end free to move with expansion andcontraction of said device, a shaft, 9. flexible strand wrapped aroundsaid shaft, a support connected to the free end of said device andhaving two terminals on opposite sides of said shaft, means foryieldably holding said strand under tension between said terminals, anda temperature control device operated by said shaft.

AUGUST A. STRAND.

